In this Thursday, Sept. 27, 2012 file photo, students walk through the University of Texas at Austin campus in Austin, Texas. This giant flagship campus - once slow to integrate - is now among the most diverse in the country. (AP Photo/Eric Gay, File)

In post-Great Recession America, which is the bigger barrier to opportunity — race or class?

A decade ago, the U.S. Supreme Court kept the focus on race as a barrier, upholding the right of colleges to make limited use of racial preferences to ensure a diverse student body. But in a ruling due this month, the court is widely expected to roll back that decision. Such an outcome would shift attention more toward a less constitutionally controversial practice: giving a boost to socio-economically disadvantaged students, regardless of race.

If that happens, it would reflect more than just a more conservative makeup of the justices. Over the last decade, clogged social mobility and rising economic inequality have shifted the conversation on campuses and in the country as a whole.

As a barrier to opportunity, class is getting more attention, while race is fading.

"The cultural zeitgeist has changed," said Peter Sacks, author of the book "Tearing Down the Gates: Confronting the Class Divide in American Education."

"The Great Recession really exacerbated the vast and growing inequalities between rich and poor in America," he said. "Talking openly about class has been taboo," he added, but in recent years the evidence of widening inequality has mounted and it's become "OK for the so-called 99 percent to talk about the 99 percent."

The shift is perceptible in a range of ways:

—You can see it in polling, like surveys from the Pew Research Center, which shows the percentage of Americans who feel racial discrimination is the chief impediment to black progress is falling, from 37 percent in 1995 to 23 percent in 2012.

Polling on affirmative action varies widely depending on how questions are phrased, but an ABC News/Washington Post poll released June 12 showed strong feelings about using race in college admissions: Just 22 percent of Americans support letting universities consider applicants' race as a factor, and 76 percent oppose the practice. The proportions supporting racial preferences were similar for blacks (19 percent) and Hispanics (29 percent) as for whites (20 percent).

—You can read it in the tone of recent opinion pieces penned even by left-leaning academics and columnists, whose support for racial preferences has eroded under a mountain of evidence that quality higher education is tilting further toward the already-wealthy.

—You can hear it, too — in conversations on elite college campuses, where the dearth of low-income students is replacing race as a topic of debate. And in the words of the first black president, who has said there's no good reason his own daughters should benefit from racial preferences when they apply to college.

The shifting debate has painted supporters of race-based affirmative action into a difficult corner. Most agree the barriers to low-income students are a serious problem that should be addressed, and of course, many minority students are also low-income.